A malocclusion is a misalignment of teeth or incorrect relation between the teeth of the two dental arches. The term was coined by Edward Angle—the father of modern orthodontics—as a derivative of occlusion, which refers to the way opposing teeth meet. Angle based his classifications of malocclusions on the relative position of the maxillary first molar. According to Angle, the mesiobuccal cusp of the upper first molar should align with the buccal groove of the mandibular first molar. The teeth should all fit on a line of occlusion, which is a smooth curve through the central fossae and cingulum of the upper canines, and through the buccal cusp and incisal edges of the mandible. Any variations therefrom results in malocclusion.
There are three classes of malocclusions, Class I, II, and III. Further, class II is subdivided into three subtypes:
Class I: Neutrocclusion Here the molar relationship of the occlusion is normal or as described for the maxillary first molar, but the other teeth have problems like spacing, crowding, over or under eruption, etc.
Class II: Distocclusion (retrognathism, overjet) In this situation, the upper molars are placed not in the mesiobuccal groove, but anteriorly to it. Usually the mesiobuccal cusp rests in between the first mandibular molars and second premolars. There are two subtypes:
Class II Division 1: The molar relationships are like that of Class II and the anterior teeth are protruded.
Class II Division 2: The molar relationships are class II but the central incisors are retroclined and the lateral incisors are seen overlapping the central incisors.
Class III: Mesiocclusion (prognathism, negative overjet) In this case the upper molars are placed not in the mesiobuccal groove, but posteriorly to it. The mesiobuccal cusp of the maxillary first molar lies posteriorly to the mesiobuccal groove of the mandibular first molar. This malocclusion is usually seen when the lower front teeth are more prominent than the upper front teeth. In such cases, the patient very often has either a large mandible or a short maxillary bone.
Orthodontics, formerly orthodontia (from Greek orthos “straight or proper or perfect”; and odous “tooth”), is the first specialty of dentistry that is concerned with the study and treatment of malocclusion, which can be a result of tooth irregularity, disproportionate facial skeleton relationship, or both. Orthodontics treats malocclusion through the displacement of teeth via bony remodeling and control and modification of facial growth.
This process has been traditionally accomplished by using static mechanical force to induce bone remodeling, thereby enabling teeth to move. In this approach, braces consisting of an archwire interfaces with brackets that are affixed to each tooth. As the teeth respond to the pressure applied via the archwire by shifting their positions, the wires are again tightened to apply additional pressure. This widely accepted approach to treating malocclusion takes about twenty four months on average to complete, and is used to treat a number of different classifications of clinical malocclusion.
Treatment with braces is complicated by the fact that it is uncomfortable and/or painful for patients, and the orthodontic appliances are perceived as unaesthetic, all of which creates considerable resistance to use. Further, the treatment time cannot be shortened by increasing the force, because too high a force results in root resorption, as well as being more painful. The average treatment time of 24-months is very long, and further reduces usage. In fact, some estimates provide that less than half of the patients who could benefit from such treatment elect to pursue orthodontics.
Kesling introduced the tooth positioning appliance in 1945 as a method of refining the final stage of orthodontic finishing after removal of the braces (debanding). The positioner was a one-piece pliable rubber appliance fabricated on the idealized wax set-ups for patients whose basic treatment was complete. Kesling also predicted that certain major tooth movements could also be accomplished with a series of positioners fabricated from sequential tooth movements on the set-up as the treatment progressed. However, this idea did not become practical until the advent of 3D scanning and computer modeling in 1997, when the Invisalign® system was introduced by Align Technologies®.
Removable clear appliances, such as Invisalign®, OrthoClear®, ClearAligner® and ClearCorrect®, provide greatly improved aesthetics since the devices are transparent. However, because these appliances can be removed, compliance can be an issue, and failure to use the device slows overall treatment time. The success of clear aligners is predicated on a patient's commitment to wear the aligners for a minimum of 20-22 hours per day, only removing them to eat, drink, and brush the teeth.
As a treatment modality, aligners are also limited in the classifications of clinical malocclusion that they can address. In the past, aligners have not been able to easily rotate or extrude teeth because the aligner cannot adequately direct force in all directions. Conditions that can be difficult to treat or are contra-indicated for treatment with clear aligners include:                crowding and spacing over 5 mm        skeletal anterior-posterior discrepancies of more than 2 mm (as measured by discrepancies in cuspid relationships)        centric-relation and centric-occlusion discrepancies        severely rotated teeth (more than 20 degrees)        open bites (anterior and posterior) that need to be closed        extrusion of teeth        severely tipped teeth (more than 45 degrees)        teeth with short clinical crowns        arches with multiple missing teeth.        
Being aware of the aligner limitations, Align Technologies® has recently combined the clear aligners with clear attachments or posts that adhere to teeth and provide a surface on which force can be exerted in the desired direction. A custom mold is made using a 3D model of the patients teeth with pockets therein for the placement of a force attachment, the placement and shape of which are determined using proprietary modeling software. The relevant force attachments are made and fitted into the mold, adhesive applied to the attachments, and the mold applied to the teeth. This allows precise and quick placement of the clear attachments, which are then affixed using light curing of the adhesive. These attachments allow the Invisalign® to tackle some of the more difficult orthodontic problems, including directing force to a tooth that needs to be further extruded.
There is some affect on aesthetics, but because the force attachments are also clear, they are less noticeable from a distance. However, the aesthetics could be improved. Even the original clear aligner aesthetics could be improved because in use they produce a noticeable clear line under the teeth, which is easily seen when the patient is smiling (see FIG. 2A-B).
Yet another option is to combine the features of a clear aligner with some of the advantages of traditional appliance technology. Clear Fusion® Orthodontic Appliances, for example, combines Hawley appliances with clear aligner technology. For example, a rapid palatal expander can be combined with a clear aligner that interfaces with part of the dentition. Further, many practitioners have manually combined the aligner with various appliances, especially to treat class II malocclusions.
In addition to malocclusion, many patients have discolored or damaged teeth surfaces that need repair. The outer covering of the visible part of the tooth (the crown) is enamel, which is translucent and is white or bluish white or grey by itself, but with dentin underneath can vary in color from yellowish to grayish white. It is the hardest tissue in the human body and can endure crushing pressure of approximately 100,000 pounds per square inch. It consists of approximately 96% inorganic minerals—calcium and phosphorus (as hydroxyapatite)—as well as 1% organic materials and 3% water.
Like pearls, enamel is birefringent (thus can split a light beam into two colors) and has a refractive index of about 1.5-1.6 (in comparison porcelain is 1.5 and quartz is 1.54). However, refractive index will vary between patients, with wavelength used, the condition of the enamel, and with the measuring system used. Using optical coherence tomography (OCT), one group obtained the refractive index of dental enamel to be 1.631+/−0.007. Meng Z, et al., Measurement of the refractive index of human teeth by optical coherence tomography, J Biomed Opt. 14(3):034010 (2009).
Veneers are an important tool used to cover discolored or damaged teeth. A dentist or orthodontist may use one veneer to restore a single tooth that may have been fractured or discolored, or multiple teeth to create a “Hollywood” type of makeover. In terms of aesthetics, the ultimate in cosmetic dentisry is the porcelain veneer and/or crowns. Porcelain is a ceramic material made by heating raw materials, generally including clay in the form of kaolin, in a kiln to temperatures between 1,200° C. (2,192° F.) and 1,400° C. (2,552° F.). The toughness, strength, and translucence of porcelain arise mainly from the formation of glass and the mineral mullite within the fired body at these high temperatures. Porcelain has the translucent, yet white, appearance of real enamel, yet is longer lasting and more durable than the less expensive resins.
Clear aligners have been a tremendous improvement in orthodontic practice, as evidenced by their increasing market share and popularity with adult and to a lesser extent, teen, patients. However, further improvements in the aligner technology are always beneficial, and this application addresses some of those improvements. Improvements in aesthetics are particularly needed, because one of the most important impediments to orthodontic treatment is the perceived poor aesthetics during treatment, especially in teen and adult populations. See e.g., Klages, U., et al., American Journal of Orthodontics and Dentofacial Orthopedics 128(4): 442-449 (2005) (“favorable dental esthetics and previous orthodontic treatment might be important variables in explaining individual differences in oral-health attitudes and behaviors.”).